This invention is a centrifugation chamber for the separation of suspended particles by buoyant density gradient centrifugation.
Separation of biological particles such as cells, organelles and macromolecules by utilizing either differences in their buoyant densities or in particle sizes is a well-established biomedical method.
Buoyant density gradient centrifugation is used to separate particles of different densities. Centrifuge tubes containing volumes of about 10 through 50 ml are commonly used for this purpose.
Since density gradients become increasingly unstable in larger tubes and swirling occurs on acceleration and deceleration of the centrifuge, tubes of larger volumes can hardly be used even for preparative purposes.
To separate large volumes of material it is necessary to distribute aliquots into a number of small gradient tubes, which is time consuming.
Different types of zonal rotors can be used for large-scale density gradient centrifugation, but these are expensive and additional equipment, such as special pumping devices, is required.
Receptacles and devices for centrifugation which are subdivided into two or more compartments are disclosed in U.S. Pat. No. 3,456,876 and DE-OS 1,648,844 (Fed. Rep. of Germany). The subdivisions are thought to reduce the path length of sedimentation for pelleting very small particles, particularly of particles with sedimentation rates of less than 10.sup.2 Svedberg units, such as biological macromolecules, resulting in an overall reduction of centrifugation time required to pellet these particles. ("Svedberg unit" is a commonly used metric unit in centrifugation, having the dimension of 10.sup.-13 sec.)
These devices, however, are designed to pellet, i.e. sediment, very small particles by (ultra)-centrifugation and are not suitable for density gradient centrifugation. Compared to other parameters, buoyant density, the major criterion in density gradient centrifugation, is of minor importance for pelleting.
The objective of the present invention is to provide a device for large scale density gradient centrifugation (volume: over one hundred milliliters up to several liters), which is simple, effective and which can be used in combination with large laboratory centrifuges and the appropriate standard swinging-bucket rotors, which are widely available.
The density gradient has to be mechanically stable and unwanted swirling should be effectively prevented. In particular, the density gradient has to be sufficiently stable to withstand the rotational forces which occur during acceleration and deceleration of the centrifuge and which tend to cause unacceptable vortices in large volume gradient tubes.
In general, the objectives of the invention are accomplished by subdividing one large centrifugation chamber by means of stabilizing walls or lamellae into several compartments which are geometrically arranged as described below. The characteristic features of this invention are the walls which lie in radially and vertically oriented planes during centrifugation, i.e. in planes which are defined by both the direction of the centrifugal force and the axis of rotation.
Other features and advantages of the invention will be apparent from the following description of a preferred embodiment and from the claims.